Flux Calibration and Extinction Properties from the Nearby Supernova Factory
Résumé
The Nearby Supernova Factory has discovered and observed in detail a large sample of Type Ia supernovae using the dedicated Supernovae Integral Field Spectrograph (SNIFS). This custom-built spectrograph has been in operation since 2004 on the Univeristy of Hawaii 2.2-m telescope on Mauna Kea. To reach the targeted spectrophotometric accuracy, attention has been focused on several key aspects of the calibration procedure, including: estimating the nightly photometric quality, derivation of the nightly sky extinction over the extended optical domain (320-1000 nm), its modeling in terms of physical components (Rayleigh and aerosol scattering, ozone absorption and telluric lines) and its variability within a given night. For this purpose, an optimal algorithm has been implemented to analyze atmospheric conditions from approximately 2300 observations of spectrophotometric standard stars taken throughout the night over nearly 300 individual nights.